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feat(eslint-plugin): [restrict-plus-operands] add intersection type determination logic #2628

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merged 6 commits into from Oct 18, 2020

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sunghyunjo
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Fixes #2506

@typescript-eslint
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Thanks for the PR, @sunghyunjo!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!


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codecov bot commented Oct 2, 2020

Codecov Report

Merging #2628 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2628   +/-   ##
=======================================
  Coverage   92.82%   92.82%           
=======================================
  Files         293      293           
  Lines        9619     9622    +3     
  Branches     2697     2698    +1     
=======================================
+ Hits         8929     8932    +3     
  Misses        326      326           
  Partials      364      364           
Flag Coverage Δ
#unittest 92.82% <ø> (+<0.01%) ⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files Coverage Δ
.../eslint-plugin/src/rules/restrict-plus-operands.ts 100.00% <ø> (ø)

@bradzacher bradzacher added the enhancement: plugin rule option New rule option for an existing eslint-plugin rule label Oct 2, 2020
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lgtm - thanks for your contribution!

Comment on lines +73 to +76
if (type.isIntersection()) {
const types = type.types.map(getBaseTypeOfLiteralType);
return types.some(value => value === 'string') ? 'string' : 'invalid';
}
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it took me a second to figure out why this works for valid cases.
For the weird cases we care about (like {} & string), typescript tells us the type is an intersection type.

For other cases like unknown & string, typescript tells us the type is just string!
And for bad cases like number & string, typescript again tells us the type is just never!

This is pretty awesome! 😄

@bradzacher bradzacher merged commit da71362 into typescript-eslint:master Oct 18, 2020
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[restrict-plus-operands] false positive on types like {} & string
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